Wireless medium is limited in bandwidth. To keep the medium clear, it is preferred to eliminate unnecessary multicast traffic when there is a need. Dynamic multicast optimization (DMO), which consumes less bandwidth by converting multicast traffic to unicast, ensures higher priority treatment for reliable over-the-air delivery.
In a current approach for DMO, a static threshold is predetermined to control the conversion from multicast to unicast. For example, a threshold for the number of subscribers (clients) associated with one access point (AP) is preset and only if the number of subscribers of the multicast traffic is fewer than the threshold, the approach converts the multicast traffic to unicast. The threshold based approach simplifies the process and might results in decent performance in simple scenarios.
The threshold based approach, nevertheless, suffers significant challenges. This approach, which is load ignorant even if the number of clients is fewer than the preset threshold, is, therefore, incapable of adapting to time varying traffic load and can result in unintentional deterioration in performance (e.g., increased delay and jitter) when the overall traffic increases. Specifically, for real time multicasts, where delay and jitter play an important role in determining quality of a call or reception of video, link adaption with change in perceived load is a must. Further, due to bursty and continuous time varying traffic, it is inherently difficult for the threshold based approach to predict the load and preset the threshold accordingly. It is not possible to set even a conservative threshold since it may result in counter-productive performance under different network loads.
Moreover, with the advent of 802.11ac links, the coexistence of legacy clients will result in a higher disparity in client capabilities and this need to be taken into account while deciding when a multicast group can be converted to unicast. The current approach also does not take Quality of Service (QoS) into account. For all types of multicast traffic, the current approach makes a conversion decision in the same fashion, which can degrade performance for video or voice multicasts. Furthermore, the current approach does not take interference or link quality to clients into account.
Typically, clients (stations) associate with one multicast group have different capabilities in terms of transmission rates, physical locations and link qualities, etc. Thus, a mechanism which is able to account for these aspects will be able to benefit from the information.